1. Field of the Invention
The present invention relates to a satellite broadcast reception system. More particularly, the present invention relates to a satellite broadcast reception system that can receive individually with a plurality of satellite receivers a plurality of satellite broadcasting signals received from a plurality of satellites.
2. Description of the Background Art
Referring to FIG. 8, communication satellites (CS) called JCSAT3 and JCSAT4 are launched at 128xc2x0 and 124xc2x0 of east longitude up in the sky over Japan. The satellite broadcasting signal transmitted by respective satellites are formed of the two types of signals of a horizontally polarized wave and a vertically polarized wave. The antenna for receiving a satellite broadcast that can receive satellite broadcasting signals transmitted from the two satellites includes a reflector dish 6 reflecting the satellite broadcasting signal transmitted by the two satellites, and an LNB (Low Noise Block Down Converter) 58 that amplifies the low noise of a satellite broadcasting signal reflected at reflector dish 6 and converts the frequency down to a low frequency band. A receiver of a satellite broadcasting signal such as a television receiver 60 is connected to LNB 58.
Referring to FIG. 9, a conventional LNB 58 includes an LNA (Low Noise Amplifier) 62 receiving horizontally and vertically polarized wave signals transmitted from JCSAT3 and horizontally and vertically polarized wave signals transmitted from JCSAT4 to amplify the low noise of either signal according to an output of a power supply circuit 68 that will be described afterwards, a BPF (Band Pass Filter) 64 connected to LNA 62 to receive the output of LNA 62 as an input, a local oscillator 26 generating a local oscillator signal of 11.2 GHz, a mixer 30A connected to BPF 64 and local oscillator 26 to mix the local oscillator signal with the signal output from BPF 64 to provide an IF (Intermediate Frequency) signal, an IF amplifier 66 connected to the output of mixer 30A to amplify an IF signal, and a capacitor 35A connected to the output of IF amplifier 66 to cut the noise of low frequency. Capacitor 35A is connected to the output terminal of an IF signal. The IF signal output terminal has the foregoing receiver connected to the end.
LNB 58 further includes a power supply circuit 68 connected to the IF signal output terminal to receive direct current DC from the IF signal output terminal and a low frequency pulse signal AC of an alternating current of several ten KHz overlying direct current DC to supply desired power to a semiconductor amplify element forming LNA 62 according to the voltage value of direct current DC and the presence of low frequency pulse signal AC. Power supply circuit 68 also supplies power to each component forming LNB 58 besides LNA 62.
LNA 62 includes semiconductor amplify elements 63A and 63B receiving the horizontally polarized wave signal and vertically polarized wave signal transmitted from JCSAT3 as respective inputs, semiconductor amplify elements 63C and 63D receiving the horizontally polarized wave signal and vertically polarized wave signal from JCSAT4 as inputs, respectively, and a semiconductor amplify element 63E connected to the outputs of semiconductor amplify elements 63A-63D.
The voltage value of direct current DC supplied from the IF signal output terminal includes the two types of 18 V and 13 V. When the voltage value of direct current DC is 18 V, a horizontally polarized wave signal is selected. When the voltage value of direct current DC is 13 V, a vertically polarized wave signal is selected. In the case direct current DC is overlaid over low frequency pulse signal AC, JCSAT3 is selected. When direct current DC is not overlaid over low frequency pulse signal AC, JCSAT4 is selected.
For example, in the case where direct current DC of 13 V overlaid with low frequency pulse signal AC is supplied to power supply circuit 68 from a receiver connected to the IF signal output terminal, the receiver selects the vertically polarized wave signal transmitted from JCSAT3. Therefore, power supply circuit 68 supplies power to semiconductor amplify elements 63B and 63E forming LNA 62. Power is not supplied to semiconductor amplify elements 63A, 63C and 63D. Thus, the vertically polarized wave signal transmitted from JCSAT3 has the low noise amplified by semiconductor amplify elements 63B and 63E. The low-noise amplified signal is applied to BPF 64 to have the image signal removed. Mixer 30A mixes the local oscillator signal generated at local oscillator 63 with the signal output from BPF 64 to provide an IF signal. IF amplifier 66 amplifies the IF signal. The amplified IF signal has the noise of the low frequency cut at capacitor 35A, and then output from the IF signal output terminal.
Accordingly, one of the two satellites is selected, and one of the two types of polarized wave signals transmitted from the selected satellite is selected. The selected polarized wave signal has the low noise amplified and frequency converted to be output from the IF signal output terminal.
LNB 58 has only one IF signal output terminal. Therefore, the signal output from LNB 58 is limited to one polarized wave signal transmitted from one satellite. This means that only one receiver can be connected to one LNB 58. A plurality of television receivers or video recorders cannot be connected thereto.
The satellite is selected based on the presence of low frequency pulse signal AC. Therefore, one LNB 58 can only receive the satellite broadcasting signals from two satellites. It was difficult to receive satellite broadcasting signals from three or more satellites.
If a satellite can be selected by digital serial data instead of the presence of a low frequency pulse signal AC, information of what type of polarized wave signal from which satellite has been selected can be processed by providing an apparatus that can process digital data such as a personal computer at the receiver side.
In view of the foregoing, an object of the present invention is to provide a satellite broadcast reception system that can have a plurality of receivers connected.
Another object of the present invention is to provide a satellite broadcast reception system that can receive a satellite broadcasting signal from at least three satellites.
A further object of the present invention is to provide a satellite broadcast reception system that can process information related to selection of a satellite and a polarized wave signal.
A low noise block down converter according to an aspect of the present invention includes a conversion unit receiving a plurality of types of polarized wave signals transmitted from each of a plurality of satellites to convert a plurality of polarized wave signals into a plurality of intermediate frequency signals, an amplify switch connected to the conversion unit with a plurality of intermediate frequency signals as inputs, and having a plurality of outputs connected to a plurality of output ports, respectively to determine a status according to a select signal and providing an amplified intermediate frequency signal, and a first control unit receiving external digital serial data to select a satellite via an output port and providing a select signaled according to the digital serial data.
The plurality of types of polarized wave signals transmitted from respective plurality of satellites are converted into intermediate frequency signals and then applied to the amplify switch. The first control unit receives external digital serial data via the plurality of output ports to apply a select signal to the amplify switch. The amplify switch receives a select signal for each output to provide a polarized wave signal according to the select signal. Therefore, a plurality of polarized wave signals are output from one low noise block down converter. The plurality of polarized wave signals can be selected independently by an external source through the plurality of output ports. Therefore, a plurality of satellite receivers can be connected to one low noise block down converter. Each of the plurality of satellite receivers can select a polarized wave signal independently. It is not necessary to install a low noise block down converter for each satellite differing in the orbit position.
Preferably, the converter unit includes a plurality of low noise amplifiers provided corresponding to each of the plurality of satellites, each low noise amplifier receiving a plurality of types of polarized wave signals to amplify low noise, a plurality of filters connected to the plurality of low noise amplifiers to remove an image signal from the low-noise amplified plurality of types of polarized wave signals, a local oscillator generating a local oscillator signal, a plurality of buffer amplifiers provided corresponding to each of the plurality of satellites, connected to the local oscillator to amplify a local oscillator signal, and a plurality of mixers provided corresponding to each of the plurality of satellites, and connected to a filter and a buffer amplifier corresponding to the satellite to mix the local oscillator signal with the plurality of types of polarized wave signals removed in image signals to output an intermediate frequency signal.
A buffer amplifier is connected between the local oscillator and the mixer in each satellite. Therefore, leakage of an RF (Radio Frequency) signal of a satellite to the RF signal of another satellite can be suppressed. The isolation of the RF signals between different satellites can be improved.
Further preferably, the amplify switch includes a switch having a plurality of outputs, connected to the conversion unit with a plurality of intermediate frequency signals as the inputs to define a status according to a select signal, and an amplifier unit connected to the switch, having a plurality of outputs connected to the plurality of output ports, respectively, to amplify respective plurality of outputs of the switch.
Following selection of an intermediate frequency signal by the switch, the selected signal is amplified. Therefore, the number of components forming the amplifier unit can be reduced than the case where the intermediate frequency signal is amplified at a preceding stage of the switch.
Further preferably, the amplifier unit includes a plurality of amplifiers connected to the plurality of outputs of the switch, respectively, to amplify the plurality of outputs, and a plurality of constant voltage regulators receiving power from an external source via a plurality of output ports to supply the power to the plurality of amplifiers.
A constant voltage regulator is provided for each amplifier. In the case where power is not supplied from the output port, the amplifier connecting to that output port is not supplied with power. Therefore, the power consumption of the low noise block down converter can be reduced.
Further preferably, the first control unit includes a second control unit receiving from an external source through the output port digital data to select a satellite and a direct current having a voltage value corresponding to the type of the polarized wave signal to output a select signal according to the digital serial data and the voltage value of the direct current.
A polarized wave signal can be selected according to the direct current having a predetermined voltage value. Thus, compatibility with a conventional satellite receiver can be maintained.
Further preferably, the low noise block down converter includes a power switch connected to a plurality of output ports to select any of the output ports according to a control signal for connection with the output, and a constant voltage power supply circuit connected to the power switch, receiving direct current output from the power switch to supply to the conversion unit and the second control unit power subjected to constant voltage conversion. The second control unit includes a select signal output unit providing a select signal according to digital serial data and the voltage value of the direct current, and a control signal output unit providing a control signal according to the digital serial data and the voltage value of the direct current.
The control signal output unit provides a control signal according to digital serial data and the voltage value of the direct current. The power switch selects any of the plurality of output ports according to the control signal. Digital serial data and direct current are supplied to the constant voltage power supply circuit from a satellite receiver through the selected output port. Digital serial data and constant current are not supplied from the other output ports. Therefore, even in the case where the voltage of the selected satellite receiver changes, that voltage change will not affect the digital serial data and the like transmitted from other satellite broadcast receiver. As a result, voltage drop will not occur at the output port connected to another satellite receiver. Also, false digital serial data caused by voltage drop will not occur. Therefore, the low noise block down converter can be operated stably without erroneous operation.
A satellite broadcast receiver according to another aspect of the present invention is input with an intermediate frequency signal according to a wave from a satellite through an input port. The satellite broadcast receiver includes an intermediate frequency signal conversion unit deriving and providing a video signal and an audio signal by the intermediate frequency signal input to the input port, an input unit through which a select signal to select a satellite is input, and a digital serial data supply unit connected to the input unit to supply digital serial data to select a satellite to the input port according to a select signal.
A satellite is selected by the digital serial data. By setting the number of bits of the digital serial data used in the selection of a satellite to at least 2 bits, a satellite broadcasting signal can be received from at least three satellites.
Preferably, the intermediate frequency signal conversion unit includes a videoxe2x80xa2audio signal extraction unit extracting and providing a video signal and audio signal from an intermediate frequency signal, and a reception signal information output unit providing reception signal information representing a reception status of a satellite from the intermediate frequency signal. The satellite broadcast receiver further includes a status signal output unit connected to the input unit and the reception signal information output unit to output a select signal and reception signal information.
A select signal and reception signal information are output from the status signal output unit. By connecting a personal computer to a satellite receiver, or by incorporating a personal computer in a satellite broadcast receiver, the status of the satellite, the reception status, and the like can be supervised according to a computer program. Therefore, past record information such as how long a viewer has watched a certain program can be obtained. When the viewer is not watching a program, the computer program can be downloaded from a satellite. Therefore, the maintenance and service of the system of the personal computer can be improved.
According to a further aspect of the present invention, a satellite broadcast reception system includes the above-described low noise block down converter, and a satellite receiver connected to the low noise block down converter for usage.
A plurality of types of polarized wave signals transmitted from respective plurality of satellites are converted into intermediate frequency signals and then applied to an amplify switch. A first control unit receives external digital serial data through a plurality of output ports and applies a select signal to the amplify switch. The amplify switch receives a select signal for each output to output a polarized wave signal according to the select signal. Therefore, a plurality of polarized wave signals are output from one low noise block down converter. The plurality of polarized wave signals can be selected independently by an external source through the plurality of output ports. Therefore, a plurality of satellite receivers can be connected to one low noise block down converter. The plurality of satellite receivers can select a polarized wave signal independently. It is not necessary to install a low noise block down converter individually for each satellite differing in orbit position.
Preferably, the satellite broadcast system includes the above-described satellite receiver.
A satellite is selected by digital serial data. By setting the number of bits of the digital serial data used in selecting a satellite to at least 2 bits, satellite broadcasting signals from at least three satellites can be received.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.